In the past, there has been proposed an ultrasonic wave device which is configured to transmit ultrasonic waves and receive ultrasonic waves reflected by an obstacle. This kind of ultrasonic wave device, for example, detects presence or absence of an obstacle on the basis of information whether the ultrasonic wave device has received a reflected wave which was generated due to reflection of a transmitted ultrasonic wave by the obstacle. Moreover, this kind of the ultrasonic wave device, for example, detects a distance to the obstacle on the basis of the time from transmitting the ultrasonic wave to receiving the reflected wave (for example, JP 4056568 B2).
The ultrasonic wave device mentioned above is used by being attached to a bumper 1A of a vehicle, as shown in FIG. 15 and FIG. 16.
In detail, the ultrasonic wave device mentioned above includes a holding member 2A designed to be fixed to an inner surface of the bumper 1A by gluing or welding, and a body block 3A. The body block 3A has an exposed surface 30A through which ultrasonic waves are input and output, and is held in the holding member 2A. The bumper 1A has an exposing hole 11A that exposes the exposed surface 30A of the body block 3A, and the body block 3A includes a head 31A including the exposed surface 30A and designed to be inserted into the exposing hole 11A. A dimension and a shape of the head 31A are designed so that the exposed surface 30A is to be flush with an outer surface of the bumper 1A, as shown in FIG. 16.
However, when a periphery of the exposing hole 11A is curved in the bumper 1A, a positional relationship between a portion of the holding member 2A abutting on the bumper 1A (a mounting surface) and an opening surface of the exposing hole 11A changes depending on a degree of curvature of the periphery. Thereafter, a holding ring 7A interposed between the body block 3A and the bumper 1A becomes deformed and a depth of insertion of the head 31A to the exposing hole 11A changes. Hence, the exposed surface 30A becomes not to be flush with the outer surface of the bumper 1A, and it affects an appearance.
For example, when the bumper 1A is curved so as to swell a vicinity of the exposing hole 11A outward, the portion of the holding member 2A abutting on the bumper 1A becomes positioned further inward from an opening of the exposing hole 11A in a normal direction of the exposed surface 30A, and the exposed surface 30A thereby becomes more depressed than a case in which the bumper 1A is flat. Conversely, when the bumper 1A is curved so as to hollow an outer surface of the vicinity of the exposing hole 11A, the portion of the holding member 2A abutting on the bumper 1A becomes positioned further outward from the opening of the exposing hole 11A in the normal direction of the exposed surface 30A, and the exposed surface 30A thereby becomes more protruded than the case in which the bumper 1A is flat.